Context Menus

To use context menus, you need to right click your target and click on Apps, as can be seen in the picture. You will then see all available commands for your target.
ContextMenuGuide
Message Context Menus
Only Available in the Descend Server
Add Emoji

Add the selected image to the guild as an emoji

Draw Giveaway Winner

Close the giveaway and draw a winner from the giveaway. Use multiple times if you want multiple winners

Available Globally
Get Timestamps

Format all (relative) dates and times in the message

User Context Menus
Available Globally
Get Join Code

Gets the selected users Destiny 2 join code, like /join Name#1234

Unless otherwise specified, commands are not available in DMs.